Calf Study to Examine Endostaple Related Thrombogenesis and Tissue In-growth

BACKGROUND:
In order to achieve secure attachment of a prosthetic graft to an artery it is well established that the prosthetic graft be attached to the full thickness of the arterial wall. Most commercially available endografts rely on friction and columnar non-compressability to provide endograft attachment to the aortic neck just below the renal arteries. While this approach works in many instances, there is still a 4% per year complication rate that requires reintervention as well as a 1% aneurysm rupture rate. Moreover, proximal type one endoleak remains a concern. The purpose of this study was to assess the ability of Endostaples to attach a patch graft to the thoracic aorta of calves.
METHODS:
To assess tissue ingrowth into the Endostaple and any thrombus formation after insertion into an aortic wall, an arterial prosthetic graft was attached in a patch fashion to an oval opening in the descending aorta in 11 calves. Two thirds of the suture line was achieved using 5-0 polypropylene sutures and one third of a contiguous segment was achieved solely with Endostaples inserted using a holmium YAG laser in each calf. Seven calves were sacrificed at 30 days and four at 90 days. Histopathological examination was performed on all 11 specimens.
RESULTS:
Histopathological examination demonstrated excellent tissue ingrowth into and throughout all Endostaples. There was no residual thrombus on the graft suture line or the Endostaple line. The inflammatory changes observed, typical of a healing graft/arterial attachment, elicited by the Endostaple line were equal or less than those observed by the suture line. No observable differences were noted between the one and the three month animals and between those that had one row of Endostaples inserted and those that had a double row (to determine if the Endostaples might cause tissue necrosis if many were placed close together). No Endostaple failed to hold the graft to the aortic wall and there was no evidence of any separation of the prosthetic graft from the aortic wall. All of the 92 tested Endostaples had complete tissue ingrowth into the interstices of the Endostaple (markedly reducing the ability of the staple wire to be subjected to flex forces).
CONCLUSIONS:
A coiled coil Endostaple appears to be equivalent to standard vascular suture in attaching prosthetic material to the full thickness of the thoracic aorta in calves. This appears to have considerable promise in improving endograft attachment. Moreover, it is likely that enhanced attachment will provide an opportunity for improved endograft design.